The invention relates to a rigid line for a brake, fuel or hydraulic system in motor vehicles, with an interior pipe which is surrounded by a layer of synthetic cladding.
Great demands are made on the rigid lines of brake, fuel or hydraulic systems in motor vehicles. They must be resistant to brake fluid, fuel or hydraulic fluid and to environmental influences to which they are exposed. Furthermore, it must be possible to subject them to high pressures and they must be corrosion-resistant over a time span of more than 10 years.
In order to meet these demands, rigid lines provided with several layers are used. Rigid lines are known that have an interior pipe of aluminum or steel which, for reasons of corrosion protection, is coated with a thermoplastic material. Furthermore, rigid lines are known whose interior pipe consists of a synthetic material which is coated on its exterior with a thermoplastic synthetic material.
It is the task of the invention to provide rigid lines for a brake, fuel or hydraulic system in motor vehicles, which are surrounded by a synthetic cladding providing increased resistance to corrosion, wherein the abrasion behavior of the synthetic cladding is improved and the mechanical strength of the rigid lines is further increased.
In accordance with the invention, this task is achieved by a rigid line for a brake, fuel or hydraulic system in motor vehicles, with an interior pipe which is surrounded by a synthetic cladding layer, wherein fibers are contained in the synthetic cladding layer.
These fibers have very high tensile strength so that the penetration of pointed objects, for example, stone chips which are flung up by the wheels of the motor vehicle when the vehicle is in motion is made more difficult. As a result, the danger of the synthetic cladding layer being damaged, thereby subjecting the interior pipe to an unimpeded corrosion attack, is reduced. Also, the fibers improve the abrasion behavior of the synthetic cladding layer and, moreover, particularly when the interior pipe is made of a synthetic material, are able to increase the strength of the rigid line.
As a supplement to the invention, it is provided that the synthetic cladding layer consist of polyethylene, so that the synthetic cladding layer can absorb the energy of impacting stones or the like to a high degree, whereby the penetration of the metallic surface by the stones is prevented.
With this variant of the invention, it is provided that an intermediate layer be present between the interior pipe and the synthetic cladding layer so that the adhesion of the synthetic cladding layer to the interior pipe is improved.
In the case of other embodiments of the invention, the interior pipe consists of a metallic material, particularly aluminum, so that a high resistance to pressure of the rigid line is achieved and, furthermore, the rigid line can be bent easily and can be worked in other ways.
As a supplement to the invention, it is provided that an olive-chromating be used as an intermediate layer so that a particularly good adhesion of the synthetic cladding layer to an interior pipe made of steel is achieved. Furthermore, the olive-chromating acts as an additional corrosion protection layer, so that the resistance to corrosion of the rigid line is further improved.
In another embodiment of the invention, a primer is used as an intermediate layer, so that a good adhesiveness between the interior pipe and the layer of synthetic cladding is achieved.
As a supplement to the invention, it is provided that the interior pipe consist of an electrically conductive synthetic material, so that no corrosion problems occur and, on the other hand, an electrostatic charging of the interior pipe can be safely prevented by grounding. The use of an electrically conductive synthetic cladding layer also makes possible the. grounding of the rigid line of the invention when the latter is connected via electrically conductive connectors with other rigid lines or other components of the brake, fuel or hydraulic system.
In another variant of the invention, a gas-tight synthetic material is used as an intermediate layer, so that liquid in the interior pipe cannot escape in the form of gas and, in this way, no emissions can be released.
As a supplement to the invention, it is provided that the fibers consist of glass, so that the strength of the synthetic cladding layer and its resistance to abrasion is clearly increased. Also, glass fibers are a relatively cost-efficient fiber material.
In another embodiment of the invention, the fibers are electrically conductive, so that the exterior surface of the rigid line can also be grounded and, in this way, static charging of the rigid line can be eliminated. This is of particular significance when combustible liquids are moved through the rigid line or may be present in the immediate vicinity of the rigid line. For the prevention of electrostatic charging by grounding the rigid line, it is sufficient when the resistance of the synthetic cladding layer amounts to one Mxcexa9/m.
In another embodiment of the invention, the fibers consist of carbon, so that an additional increase of the strength of the synthetic cladding layer is achieved and the synthetic cladding layer becomes electrically conductive.
The initially mentioned task is also solved by means of a process for the manufacture of a rigid line wherein the synthetic cladding layer is applied to the interior pipe by the extrusion of a synthetic material mixed with fibers.
The admixture of fibers to the initial material of the synthetic cladding layer increases the resistance to penetrating pointed objects and to the strength of the rigid line. Furthermore, the abrasion behavior is improved. Additionally, by means of extruding the synthetic cladding layer, a close bond between the interior pipe and the synthetic cladding layer can be achieved. This close bond can be further improved when the interior pipe is heated prior to extrusion.
As an additional advantage of the process of the invention, it must be mentioned that the process requires no additional investments in the production arrangements, since only the material of the synthetic cladding layer must be changed.
Further advantages and advantageous embodiments of the invention can be gathered from the subsequent description, the drawing and the claims.
One example of the object of the invention is shown in the drawing and is described in greater detail in the following text.